The present invention relates to the contactless charging of a battery of an electric or hybrid automotive vehicle.
Charging is performed by magnetic induction: in a location called a “charging zone”, a current is made to flow in a ground circuit possessing an emitting coil—or primary, thereby providing the power to a receiving coil—or secondary, of an electric or hybrid automotive vehicle, hereinafter simply referred to as a vehicle.
The phenomenon of magnetic induction takes place only if the primary and secondary coils are sufficiently close together, and the power transmitted depends in part on the resonance of the ground circuit. Although the vehicle is stationary when it is being charged, the frequency of the current flowing in the circuit must be adapted as a function of the position of the secondary with respect to the primary, therefore of the position of the vehicle in the charging zone with respect to the (stationary) primary. This is in order to achieve resonance of the system.
Hence more precisely, according to a first of its subjects the invention relates to a method of contactless charging of a battery of an electric automotive vehicle by magnetic induction between an emitting resonant circuit comprising an emitting coil of a charging device and a receiving resonant circuit of the vehicle comprising a receiving coil, the vehicle being positioned above the emitting coil, so as to be able to ensure good magnetic coupling between the emitting coil and the receiving coil, the method comprising steps consisting in:                commanding the electrical power supply together with the setpoints of an inverter across the terminals of which is linked the emitting coil according to a variable frequency,        measuring in an analog circuit the value of the current and of the voltage across the terminals of the emitting coil, and        computing the phase shift between the current and the voltage.        
Such a method is known to the person skilled in the art, especially through the example given thereof in the prior art document EP2317624 which is aimed especially at comparing the phases between the voltage and the current so as to drive the excitation frequency, in a circuit which comprises a “phase comparator” module, on the basis of logical signals which are images of the sign of the current and of the voltage, so as to generate a signal whose variable amplitude causes a variation of the excitation frequency by a VCO module, that is to say a voltage controlled oscillator which generates a signal whose frequency depends on the input voltage.
Other solutions consist in causing the frequency of the charging circuit to vary as a function of the power received at the secondary; but in this case, the battery of the vehicle is liable to refuse too great a transfer of power.
However, such solutions are complex and expensive to implement.